Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$66.50	6.820%	$71.0353	$71.04	$71.05	$71.00
Purchase #2	$21.53	4.657%	$22.5327	$22.53	$22.55	$22.50
Purchase #3	$100.58	9.870%	$110.5072	$110.51	$110.50	$110.50
Purchase #4	$95.30	6.767%	$101.749	$101.75	$101.75	$101.70
Purchase #5	$250.80	13.380%	$284.357	$284.36	$284.35	$284.40
Purchase #6	$180.41	8.822%	$196.3258	$196.33	$196.35	$196.30
Purchase #7	$238.90	8.798%	$259.9184	$259.92	$259.90	$259.90
7 purchase totals =	$954.02		$1,046.4254	$1,046.44	$1,046.45	$1,046.30